自己写bootloader2 -init.c,基于s3c2440

这里面主要是从拷贝代码到内存，清除BSS,还有nand的读函数。

#define NFCONF (*((volatile unsigned long *)0x4E000000))
#define NFCONT (*((volatile unsigned long *)0x4E000004))
 #define NFCMMD (*((volatile unsigned char *)0x4E000008))
 #define NFADDR (*((volatile unsigned char *)0x4E00000c))
#define NFDATA (*((volatile unsigned char *)0x4E000010))
#define NFSTAT (*((volatile unsigned char *)0x4E000020))


/*GPIO*/
#define GPHCON              (*(volatile unsigned long *)0x56000070)
#define GPHUP               (*(volatile unsigned long *)0x56000078)


/*UART registers*/
#define ULCON0              (*(volatile unsigned long *)0x50000000)
#define UCON0               (*(volatile unsigned long *)0x50000004)
#define UFCON0              (*(volatile unsigned long *)0x50000008)
#define UMCON0              (*(volatile unsigned long *)0x5000000c)
#define UTRSTAT0            (*(volatile unsigned long *)0x50000010)
#define UTXH0               (*(volatile unsigned char *)0x50000020)
#define URXH0               (*(volatile unsigned char *)0x50000024)
#define UBRDIV0             (*(volatile unsigned long *)0x50000028)


#define TXD0READY   (1<<2)
//#define UART_BRD        ((UART_CLK  / (UART_BAUD_RATE * 16)) - 1)
 void nand_read(unsigned int addr, unsigned char *buf, unsigned int len);
int Is_Boot_From_Norflash(void)
{
volatile int *p = (volatile int *)0;
int val;

val = *p;
*p = 0x12345678;

if (*p == 0x12345678)
{
/*写入内存成功，不是nor启动*/
*p = val;
return 0;
}
else
{
/*norflash 不能像内存一样写，她只能读 */

return 1;
}
}


void copy_to_sdram(unsigned char *src, unsigned char *dest, unsigned int len)
{
int i = 0;
/*如果是从nor启动，*/
if (Is_Boot_From_Norflash())
{
  while(i < len)
{
dest[i] = src[i];
i++;
}
}
else /*  否则是从nand启动*/
{
//nand_init();
nand_read((unsigned int)src, dest, len);

}


}


 void clean_bss(void)
 {
 extern int __bss_start, __bss_end;
    int *p = &__bss_start;
    
    for (; p < &__bss_end; p++)
        *p = 0;
 }


 void nand_init(void)
 {
#define TACLS   0
#define TWRPH0  1
#define TWRPH1  0

/* 设置时序 */
        NFCONF = (TACLS<<12)|(TWRPH0<<8)|(TWRPH1<<4);
        /* 使能NAND Flash控制器, 初始化ECC, 禁止片选 */
        NFCONT = (1<<4)|(1<<1)|(1<<0);
 }


 void select(void)
 {
NFCONT &= ~(1 << 1);
 }
 
 void delselect(void)
 {
NFCONT |= (1 << 1);
 }
 
void write_cmd(unsigned char cmd)
{
volatile int i ;
NFCMMD = cmd;
for(i = 0; i < 10; i++);
} 


void write_addr(unsigned int addr)
{

unsigned int col =  addr % 2048;
unsigned int page = addr  / 2048;
volatile int i;

NFADDR = col & 0xff;
for (i = 0; i < 10; i ++);
NFADDR = (col >> 8) & 0xff;
for (i = 0; i < 10; i ++);


NFADDR = page & 0xff;
for (i = 0; i < 10; i ++);
NFADDR = (page >> 8) & 0xff;
for (i = 0; i < 10; i ++);
NFADDR = (page >> 16) & 0xff;
for (i = 0; i < 10; i ++);

}


int write_data(void)
{
return NFDATA;
}




void nand_wait(void)
{
while (!(NFSTAT & 1)); 
}


 void nand_read(unsigned int addr, unsigned char *buf, unsigned int len)
 {
int i = 0;
int col = addr % 2048;
/*1: 选中芯片*/
select();
while(i < len)
{
/*2: 发出读命令00h*/
write_cmd(0x00);
/*3: 发出读地址*/
write_addr(addr);

/*4: 发出读命令30h*/
write_cmd(0x30);


/*5： 读状态*/
nand_wait();
/*6：读数据*/
for (; (col < 2048)&&(i < len); col++)
{
buf[i] = write_data();
i++;
addr++;
}


col = 0;
}
/*取消:片选*/
delselect();
 }
 
 #define TXD0READY   (1<<2)
#define RXD0READY   (1)


#define PCLK            50000000    // init.c中的clock_init函数设置PCLK为50MHz
#define UART_CLK        PCLK        //  UART0的时钟源设为PCLK
#define UART_BAUD_RATE  115200      // 波特率
#define UART_BRD        ((UART_CLK  / (UART_BAUD_RATE * 16)) - 1)


/*
 * 初始化UART0
 * 115200,8N1,无流控
 */
void uart0_init(void)
{
    GPHCON  |= 0xa0;    // GPH2,GPH3用作TXD0,RXD0
    GPHUP   = 0x0c;     // GPH2,GPH3内部上拉


    ULCON0  = 0x03;     // 8N1(8个数据位，无较验，1个停止位)
    UCON0   = 0x05;     // 查询方式，UART时钟源为PCLK
    UFCON0  = 0x00;     // 不使用FIFO
    UMCON0  = 0x00;     // 不使用流控
    UBRDIV0 = UART_BRD; // 波特率为115200
}


/*
 * 发送一个字符
 */
void putc(unsigned char c)
{
    /* 等待，直到发送缓冲区中的数据已经全部发送出去 */
    while (!(UTRSTAT0 & TXD0READY));
    
    /* 向UTXH0寄存器中写入数据，UART即自动将它发送出去 */
    UTXH0 = c;
}


void puts(char *str)
{
int i = 0;
while(str[i])
{
putc(str[i]);
i++;
}
}


void puthex(unsigned int val)
{
int i;
int j;

puts("0x");
for(i = 0; i < 8; i++)
{
j = (val >> ((7 - i) * 4)) & 0xf;
if ((j >= 0 ) && (j <= 9))
{
putc(j + '0');
}
else
{
putc('A' + j - 0xa);
}
}

声明：这些代码都是参考韦东山老师视屏写的代码。